The historical concept of bellum iustum reconsidered
After the collapse of the bipolar world order (1989/91), many military conflicts broke out in the destabilized and deeply changing world, mostly with an ethnical or islamist background. Due to this fact the focus within the concept of war has changed from the aggression of sovereign states to military violence, carried out in ethnic conflicts by non-state groups, although they often reclaim to represent “states” (as in the case of ISIS/IS). So, thereis need for a deep reform of the international public law to settle a right to intervene as a right consequence of the changes and erosions caused by ethnic conflicts and the implications to be made from the “new wars”, in order to prevent both the harm of human rights and unilateralist acts against them. The Western argument referring to the legitimacy of this kind of military intervention is based on the patristic and scholastic concept of bellum iustum (“just war”), namely on the positions of Augustine and Thomas Aquinas.
Augustine reflects upon the question, whether Christians may fight in a war or not. He comes to a positive conclusion for such cases in that the war is waged to restore peace. He modifies Jesus’ request for a radical non-violential attitude, as it is expressed in the Sermon on the Mount (Mt 5, 38-48) to an inner attitude, the praeparatio cordis, that does not demand a strict peaceful behavour in any concrete situation possible, but allows the individual to take military action, e.g. in cases of self-defense. The prerequisite of a just war in Augustine is always the transgression of the other: “Iniquitas enim partis adversae iusta bella ingerit gerenda sapienti [...]” (“Only the injustice of the other side forces the wise to just wars.”, l. XIX, c. 7). Nevertheless, the just war is a manifestation of the evil in Augustine, which may be carried out only after exhaustion of all peaceful means as an ultima reatio. Central element of the bellum iustum in Augustine is the function of the war as punishment, a concept expressed by the term iustitia vindicativa (punitive justice). Augustine builds up a bridge to the order; the Gospel teaches us about a loving attitude towards the enemy (Mt 5, 43-45). With a just war, the enemy is prevented from performing evil, an evil that contributes indirectly to the eschatological benefit of the individual’s soul, that again is orientated to the right behaviour and to God. If the enemy is not stopped doing the evil by means of war, he would go on harming God’s eternal law and sooner or later - understood eschatologically – he would be exposed to a worse punishment than those, that he should expect as worldly consequences of the war.
In Augustine the recta intentio (right intention) sets its limit on the way of warfare. According to Augustine, only such means are permitted that contribute to the fast and direct victory and the refinement of the sinner, and not those that are meant only to carry out revenge, to promote greed, and to show cruelty, because revenge, greed and cruelty do not lead to peace but to irreconcilability. The monopoly of carrying out a just war and of deciding about the applied means always lies with the state authority (auctoritas belli).
Thomas Aquinas asks whether waging war is always a sin. Among three conditions, this question has to be answered negatively: There should be an authorization by the monarch (auctoritas principis), a just reason (causa iusta) and a right intention (recta intentio) at the same time to be able to qualify a war as a bellum iustum (II-II, q. 40, a. 1). In addition to the three terms of the scholastic ius ad bellum, Aquinas mentions the debitus modus (proportional means) that became the principle of ius in bello.
On the foundation laid by Augustine and Thomas Aquinas, today's military operations can be judged as just war. The new war can only be encountered with a new international public law that forms a “new peace order” by global justice and military decision, for the new forms of violence represent challenges for the international community that need a global system of jurisdiction and execution.
Augustine. De civitate Dei. Bamberg: C. C. Buchner, 2001.
Thomas Aquinas. Summa Theologica. Rom: Marietti, 1962.